A comparative experimental study on metal active gas welding process at low temperature and room temperature

Abstract

Since the quality of the weld bead geometry depends on a number of factors that are influenced by the atmospheric conditions, much effort is being made to determine the ideal welding process parameters in order to improve the welding quality. Previous studies have solely examined the impact of process variables, such as welding current, voltage, speed, and gas flow rate, on the quality of the weld; weather conditions have not been taken into account. Atmospheric conditions during a welding process must be carefully considered, as they influence the heating and cooling rates and ultimately affect the characteristics of the welded joint. The current work includes an investigation using the metal active gas welding method on mild steel at ambient temperature and at low temperature around 0 °C. With the goal of minimizing the number of experimental runs, Taguchi's experimental design method was used to identify the process parameter settings. In addition to other crucial criteria like gas flow rate and stick out staying constant, this work took into account three welding process parameters: current (I), voltage (V), and traversal speed (S). To choose the ideal number of experiments, an experiment design based on Taguchi's L16 orthogonal array has been introduced. With constant parameters, compared to low temperature conditions, welding at room temperature resulted in notable improvements in joint characteristics: the average weld bead penetration increased by 15.02%, heat-affected zone depth by 8.23%, and bead width by 5.06%. In contrast, the average reinforcement height decreased by 4.09%. Grain refinement was observed as grain size improved by 10.4% in the weld zone and 10.14% in the heat-affected zone. Meanwhile, hardness values showed a reduction of 4.7% in the weld zone and 4.18% in the heat-affected zone. These findings emphasize that ambient environmental conditions and process parameters critically influence the thermal cycle of the weld, thereby affecting microstructure, hardness, grain morphology, and bead geometry—factors that collectively determine the mechanical integrity and overall performance of the welded joint.